It might be more semantically correct. I often use strikeout to denote done items, so in that case the semantic is different than "deleted". But you are right, in some case <del> is semantically more accurate.
– Alessandro VernetJul 16 '12 at 16:56

Came here through a google search, <del> sounds nice, esp. with a datetime attribute, but it also removed code formatting whereas <s> did not.
– notacouchNov 13 '13 at 22:51

1

Except <del> isn't Markdown; it would be HTML, if I'm not mistaken.
– SarahofGaiaSep 17 '15 at 22:58

1

@Sarah: Of course it's HTML. The answer to "Does markdown have a way to express strikeout?" is "No, but you can use some HTML to accomplish the same thing on Stack Exchange sites. Here's how..."
– aleSep 17 '15 at 23:00

@AlE.: Okay, sorry about that. My mistake. I thought the question had to do with Markdown, specifically, not just Markdown on Stack Exchange. Because some sites and Markdown editors do not support HTML, just Markdown. So I was just stating. Thanks for clarifying on that. :)
– SarahofGaiaSep 18 '15 at 18:43

@Sarah: A question about Markdown in general would be off-topic here. This site is for questions about the workings of the Stack Exchange network and the software that empowers it, thus by definition the question would have to be about the Stack Exchange flavor of Markdown.
– aleSep 19 '15 at 0:08

It may be off-topic, but since I came to this question while looking for a contextualized solution on Bitbucket and GitHub, I'd like to add the double tilde too, the only which worked in real Markdown.

Though a strike-through syntax wasn't available in the original markdown, as of today (2015), many implementations have unofficially settled on the ~(tilde) character which is supported on Reddit and as someone here mentioned, on Bitbucket too.

Let's hope Stack Overflow also adds this syntax to its Markdown implementation soon!

Why is the selected answer such a wrong and imprecise one ? !
Well, probably because people answer in comments rather than in... an answer.

Anyway.
While markdown technically doesn't support strikethrough ATM, several comments pointed out that using strikethrough in comments is possible.
Not handy, since ~ isn't supported yet, but actually possible (using unicode characters)

So, to striketrough text in questions, use the <\s> or <\del> tagsExample striked out using <\s> tagExample striked out using <\del> tag

For comments, use external converters or tools, like those websites (credits go to respective commenters)http://yaytext.com/strike/
E̶x̶a̶m̶p̶l̶e̶ ̶s̶t̶r̶i̶k̶e̶d̶ ̶o̶u̶t̶ ̶u̶s̶i̶n̶g̶ ̶y̶a̶y̶t̶e̶x̶t̶ (long strikethrough)http://adamvarga.com/strike/
E̶x̶a̶m̶p̶l̶e̶ ̶s̶t̶r̶i̶k̶e̶d̶ ̶o̶u̶t̶ ̶u̶s̶i̶n̶g̶ ̶a̶d̶a̶m̶v̶a̶r̶g̶a̶ (note the site also features an extension. I did install a similar one for GMail, once : that may be very handy.)

That's not part of markdown, just special characters, hence not a direct answer to the question here which clearly asks for a way using markdown.
– Shadow WizardNov 14 '18 at 11:45

Indeed, my bad. Guess I should move my answer to one of the other more relevant questions, like "Is strikethrough allowed in comments". Meh, my tabs are closed now... Looks like I let myself troll by the answer, which states "comment may not include strikeout" while thats not what the question was asking for. Still... looks like this means the selected answer remains a bad one, right ?
– BalmipourNov 14 '18 at 12:19

After a 2nd glance at this, the reason I answered here was clearly the selected answer. It affirms "comments may not include strikeouts", which is wrong, and shows stroke-out text without even explaining how to do it. I visited a few other threads, including the one you link here, and they fortunately got more useful answers, which is why I answered here. So I just edited my answer to precise that "While markdown technically doesn't provide strikethrough ATM, you may achieve it with unicode"
– BalmipourNov 14 '18 at 12:40